From 5c831bb1eb6b22cd1705b98188b7d1b0633e7c54 Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Tue, 7 Aug 2018 18:10:29 -0400 Subject: [PATCH] Introduce mmap_file function New in v2: - As Tom pointed out, we don't need to keep the fd around after mmapping. This simplifies things quite a bit, since we don't need a new class. It's now just a function that returns a scoped_mmap. We already have scoped_mmap, which is a thin RAII layer over mmap. If one simply wants to mmap an entire file for reading, it takes a bit of boilerplate. This patch introduces the mmap_file function to make this easier. gdb/ChangeLog: * Makefile.in (COMMON_SFILES): Add common/scoped_mmap.c. * common/scoped_mmap.c: New file. * common/scoped_mmap.h (destroy): New method. (~scoped_mmap, reset): Use destroy. (scoped_mmap): New move constructor. (mmap_file): New declaration. * unittests/scoped_mmap-selftests.c (test_normal, test_invalid_filename, run_tests): New functions. (_initialize_scoped_mmap_selftests): Register selftest. --- gdb/ChangeLog | 12 ++++++ gdb/Makefile.in | 1 + gdb/common/scoped_mmap.c | 48 ++++++++++++++++++++++++ gdb/common/scoped_mmap.h | 26 +++++++++++-- gdb/unittests/scoped_mmap-selftests.c | 54 +++++++++++++++++++++++++++ 5 files changed, 137 insertions(+), 4 deletions(-) create mode 100644 gdb/common/scoped_mmap.c diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 52e2dcb67b..970a8df832 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,15 @@ +2018-08-07 Simon Marchi + + * Makefile.in (COMMON_SFILES): Add common/scoped_mmap.c. + * common/scoped_mmap.c: New file. + * common/scoped_mmap.h (destroy): New method. + (~scoped_mmap, reset): Use destroy. + (scoped_mmap): New move constructor. + (mmap_file): New declaration. + * unittests/scoped_mmap-selftests.c (test_normal, + test_invalid_filename, run_tests): New functions. + (_initialize_scoped_mmap_selftests): Register selftest. + 2018-08-07 Simon Marchi * dwarf2read.c (read_gdb_index_from_section): Rename to... diff --git a/gdb/Makefile.in b/gdb/Makefile.in index 8c744d70c0..915e88c5fd 100644 --- a/gdb/Makefile.in +++ b/gdb/Makefile.in @@ -965,6 +965,7 @@ COMMON_SFILES = \ common/ptid.c \ common/rsp-low.c \ common/run-time-clock.c \ + common/scoped_mmap.c \ common/signals.c \ common/signals-state-save-restore.c \ common/tdesc.c \ diff --git a/gdb/common/scoped_mmap.c b/gdb/common/scoped_mmap.c new file mode 100644 index 0000000000..aa2f703fa1 --- /dev/null +++ b/gdb/common/scoped_mmap.c @@ -0,0 +1,48 @@ +/* scoped_mmap, automatically unmap files + + Copyright (C) 2018 Free Software Foundation, Inc. + + This file is part of GDB. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +#include "defs.h" +#include "scoped_mmap.h" +#include "scoped_fd.h" + +#ifdef HAVE_SYS_MMAN_H + +scoped_mmap +mmap_file (const char *filename) +{ + scoped_fd fd (open (filename, O_RDONLY)); + if (fd.get () < 0) + perror_with_name ("open"); + + off_t size = lseek (fd.get (), 0, SEEK_END); + if (size < 0) + perror_with_name ("lseek"); + + /* We can't map an empty file. */ + if (size == 0) + error (_("file to mmap is empty")); + + scoped_mmap mmapped_file (nullptr, size, PROT_READ, MAP_PRIVATE, fd.get (), 0); + if (mmapped_file.get () == MAP_FAILED) + perror_with_name ("mmap"); + + return mmapped_file; +} + +#endif /* HAVE_SYS_MMAN_H */ diff --git a/gdb/common/scoped_mmap.h b/gdb/common/scoped_mmap.h index 6070c37c40..b446163fba 100644 --- a/gdb/common/scoped_mmap.h +++ b/gdb/common/scoped_mmap.h @@ -41,8 +41,18 @@ public: ~scoped_mmap () { - if (m_mem != MAP_FAILED) - munmap (m_mem, m_length); + destroy (); + } + + scoped_mmap (scoped_mmap &&rhs) + { + destroy (); + + m_mem = rhs.m_mem; + m_length = rhs.m_length; + + rhs.m_mem = MAP_FAILED; + rhs.m_length = 0; } DISABLE_COPY_AND_ASSIGN (scoped_mmap); @@ -58,8 +68,7 @@ public: void reset (void *addr, size_t length, int prot, int flags, int fd, off_t offset) noexcept { - if (m_mem != MAP_FAILED) - munmap (m_mem, m_length); + destroy (); m_length = length; m_mem = mmap (addr, m_length, prot, flags, fd, offset); @@ -69,9 +78,18 @@ public: void *get () const noexcept { return m_mem; } private: + void destroy () + { + if (m_mem != MAP_FAILED) + munmap (m_mem, m_length); + } + void *m_mem; size_t m_length; }; +/* Map FILENAME in memory. Throw an error if anything goes wrong. */ +scoped_mmap mmap_file (const char *filename); + #endif /* HAVE_SYS_MMAN_H */ #endif /* SCOPED_MMAP_H */ diff --git a/gdb/unittests/scoped_mmap-selftests.c b/gdb/unittests/scoped_mmap-selftests.c index ece3d7a18a..d70a56a186 100644 --- a/gdb/unittests/scoped_mmap-selftests.c +++ b/gdb/unittests/scoped_mmap-selftests.c @@ -25,6 +25,7 @@ #if defined(HAVE_SYS_MMAN_H) && defined(HAVE_UNISTD_H) #include "selftest.h" +#include "common/gdb_unlinker.h" #include @@ -78,6 +79,57 @@ run_tests () } } /* namespace scoped_mmap */ + +namespace mmap_file +{ + +/* Test the standard usage of mmap_file. */ +static void +test_normal () +{ + char filename[] = "scoped_mmapped_file-selftest-XXXXXX"; + int fd = mkstemp (filename); + SELF_CHECK (fd >= 0); + + write (fd, "Hello!", 7); + close (fd); + + gdb::unlinker unlink_test_file (filename); + + { + ::scoped_mmap m = ::mmap_file (filename); + + SELF_CHECK (m.get () != MAP_FAILED); + SELF_CHECK (m.size () == 7); + SELF_CHECK (0 == strcmp ((char *) m.get (), "Hello!")); + } +} + +/* Calling mmap_file with a non-existent file should throw an exception. */ +static void +test_invalid_filename () +{ + bool threw = false; + + try { + ::scoped_mmap m = ::mmap_file ("/this/file/should/not/exist"); + } catch (gdb_exception &e) { + threw = true; + } + + SELF_CHECK (threw); +} + + +/* Run selftests. */ +static void +run_tests () +{ + test_normal (); + test_invalid_filename (); +} + +} /* namespace mmap_file */ } /* namespace selftests */ #endif /* !defined(HAVE_SYS_MMAN_H) || !defined(HAVE_UNISTD_H) */ @@ -88,5 +140,7 @@ _initialize_scoped_mmap_selftests () #if defined(HAVE_SYS_MMAN_H) && defined(HAVE_UNISTD_H) selftests::register_test ("scoped_mmap", selftests::scoped_mmap::run_tests); + selftests::register_test ("mmap_file", + selftests::mmap_file::run_tests); #endif } -- 2.34.1